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Project Notes

Test-driving Web Clients with Twisted

Using twisted for web client requests can present an “unusual” testing challenge because of the asynchronous (deferred) callback nature of twisted. And the docs aren’t that great.

So this is an exercise in writing a cannonical web client and testing it all ways I can think would normally be a “good idea”:

  • with real web requests, and the tests deal with deferred responses explicitly
  • with real web requests, but inline callbacks
  • with “mock web response”, and the tests deal with deferred responses explicitly
  • with “mock web response”, but inline callbacks

Installing Requirements

$ pip install -r requirements.txt

Running the Example

$ python timeapi/client.py
Response version: ('HTTP', 1, 1)
Response code: 200
Response phrase: OK
[('X-XSS-Protection', ['1; mode=block']),
 ('Server', ['thin 1.5.0 codename Knife']),
 ('Via', ['1.1 vegur']),
 ('Date', ['Mon, 18 Apr 2016 22:35:33 GMT']),
 ('X-Frame-Options', ['sameorigin']),
 ('Content-Type', ['text/html;charset=utf-8'])]
Response body:
2016-04-18T22:35:34+00:00

Running Tests - Trial

$ PYTHONPATH=$PYTHONPATH:$PWD trial timeapi/
timeapi.test.test_client_for_real
  TimeClientRealResponseTestCase
[...test output truncated...]

timeapi.test.test_client_mock_response
  TimeClientMockResponseTestCase
[...test output truncated...]

-------------------------------------------------------------------------------
Ran 4 tests in 1.662s

PASSED (successes=4)

Running Tests - Nose

I wasn’t sure if nosetests was going to work properly without explicitly using Twisted integration for nose.

But I haven’t needed to make any changes yet … tests run just fine with nose:

$ nosetests
..
----------------------------------------------------------------------
Ran 4 tests in 1.854s

OK

About the timeapi server

I’m using a simple time service for testing. Here’s what a raw call looks like:

$ curl -0 -i --raw http://timeapi.herokuapp.com/utc/now
HTTP/1.1 200 OK
Date: Sat, 15 Jun 2019 21:47:35 GMT
Connection: close
X-Frame-Options: sameorigin
X-Xss-Protection: 1; mode=block
Content-Type: text/html;charset=utf-8
Content-Length: 25
Server: thin 1.5.0 codename Knife
Via: 1.1 vegur

2019-06-15T22:47:36+01:00

Credits and References

About LCK#67 python
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This page is a web-friendly rendering of my project notes shared in the LittleCodingKata GitHub repository.

LittleCodingKata is my collection of programming exercises, research and code toys broadly spanning things that relate to programming and software development (languages, frameworks and tools).

These range from the trivial to the complex and serious. Many are inspired by existing work and I'll note credits and references where applicable. The focus is quite scattered, as I variously work on things new and important in the moment, or go back to revisit things from the past.

This is primarily a personal collection for my own edification and learning, but anyone who stumbles by is welcome to borrow, steal or reference the work here. And if you spot errors or issues I'd really appreciate some feedback - create an issue, send me an email or even send a pull-request.